W32/ElKern-A is an executable file virus that works under Windows 98, Windows Me and Windows 2000. It is capable of infecting file cavities, meaning that it may not change the sizes of files it infects.
Under Windows 98 and Windows Me W32/ElKern-A copies itself to the Windows System directory as the hidden file Wqk.exe, and sets the registry key:
HKLM\Software\Microsoft\Windows\CurrentVersion\Run\WQK
to point to this file so that the virus runs every time the computer is rebooted.
Under Windows 2000 W32/ElKern-A copies itself to the Windows System directory as the hidden file Wqk.dll, and sets the registry key:
HKLM\Software\Microsoft\WindowsNT\CurrentVersion\
Windows\AppInit_DLLs
to point to this file so that the virus runs every time the computer is booted.
W32/ElKern-A is carried and dropped by the W32/Klez-A worm and its variants. The virus has a destructive payload - on March 13 or September 13 the virus will overwrite files with zeros rather than infect them.